The fluorescence of 4',6-diamidine-2-phenylindole (DAPI), is enhanced by specific interaction with AT, AU, and IC double helical clusters. Our previous DAPI fluorescence decay results suggested that the lifetime heterogeneity can also originate from ground-state molecular conformers arising either from rotomer at C6 of the indole ring or at the C2. The purpose of the present work is to further investigate the mechanism of quenching of the excited state. The proton transfer hypothesis will be tested. The possibility of fast interconversion between the different solvation states will be evaluated at different pH's.